Do you think that if your members are not buying from you they are buying from someone else? Probably not. There are three potential actions that a buyer could take when they identify a need.
1. Do nothing. I have heard that ignoring the need is far more common that actually trying to solve it. There are many reasons for this. Solving it takes effort. Trying to solve a problem may mean admitting a mistake or a weakness. There could be a lack of budget or value. Perhaps they don’t know that their problem has a name or that someone else can help solve it.
2. Find a substitute. There are many ways to solve any problem. The solution that you offer is just one of those ways. While joining your association or buying one of your products may be the obvious choice to you it’s not necessarily the obvious choice to potential buyers. There’s a range of options for them to pick that may solve their problem in a totally different way than you would have.
3. Use your solution. They may buy the same product you provide from your competitor. Or they may buy it from you.
The key is telling your stories from a potential member’s/buyers point of view so they want to act, see the value of your solution and ultimatly buy from you.